Ignore Got Quattro - I'm guessing it's a male and has never been a Maid of Honour!
I've been a Maid of Honour now 3 times and a bridesmaid 2 other times. It IS hard to save the money for a trip and here's why:
1.) Must spend money to buy dress (UNLESS Bride is buying this)
2.) Must spend money to buy shoes (UNLESS Bride buys these as well)
3.) Money spent to get hair and make-up done on day of wedding (this has often been paid for by Bride's parents, but not always)
4.) Money spent on throwing friend Bridal shower (She is the Maid of Honour after all...)
5.) Bridal shower gift
6.) Wedding gift (call her appearance a present.)
7.) 2 words: Bachlorette Party.
...and there are always, ALWAYS misc. expenses that come up along the way...
You have to appreciate that it's not economical to be in a wedding! You asked her to be your Maid of Honour and your wedding is in Disney, so she will have to travel to be a part of your big day, I say you should kick in a little bit for her if she's going to come up short.
In regards to finding deals, you are a bit early for any codes or specials, you probably won't see those until end of August/September. Expedia can often offer a package deal with airfare, but unfortunately, Expedia isn't like a regular TA who can answer questions for you and make dining arrangements for you either... You get what you pay for.
Personally, I book with a TA and they hunt for the specials and codes on your behalf. A lot of people here on the DIS do it themselves, but I'm way to busy with work to even bother - I don't have time to sit on hold on the phone or even to repeatedly call, so someone else can do it for me and they make money and everyone's happy.
Good luck!